Apparatus for finishing metallic coating on a ferrous strand

ABSTRACT

Apparatus for finishing the molten metal coating on a steel core wire for ACSR wherein the strand is withdrawn from the metal bath through a close clearance, submerged die at high speed and in a non-oxidizing atmosphere. It includes a holder for the die which is free to move in any direction in a single plane and is adjustable in a plane normal to the plane of movement.

ilnite @tates Faterat Knapp Aug. 29, 1972 [54] APPARATUS FOR FHNISHING 2,238,687 4/1941 Flynn ..1 18/125 METALLHC COATKNG ()N A OUS 2,407,337 9/1946 Kolter ..1 18/ 125 STRAND 3,008,448 11/1961 Zerwes ..118/DIG. 18 3,024,762 3/1962 Zerwes ..1 18/125 [72] Invent Earle (was my, 3,060,889 10/1962 Knapp ..118/125 x [73] Assignee: Armco Steel Corporation, 3,082,119 3/ 1962 Harris ..1l7/114 C Middletown, Ohio 3,227,577 1/1966 Baessler et a1. ..1 17/ 102 M Filed: 1971 FOREIGN PATENTS OR APPLICATIONS pp 114,654 927,701 6/1963 Great Britain ..1 18/125 Related Application Data Primary Examiner-Morris Kaplan [62] Division of Ser. No. 770,566, Oct. 25, 1968, Att0rneyJohn W. Melville et al.

abandoned.

[57] ABSTRACT ((3311. Apparatus for finishing the molten metal coating on a 58] Field DIG 18 steel core wire for ACSR wherein the strand is f withdrawn from the metal bath through a close M 102 A 64 clearance, submerged die at high speed and in a nonoxidizing atmosphere. It includes a holder for the die which is free to move in any direction in a single plane [56] References cued and is adjustable in a plane normal to the plane of UNITED STATES PATENTS movement- 2,238,575 4/1941 Alexay ..1 18/125 7 Claims, 3 Drawing Figures PATENTEDwszs I972 INVENTORJS EARLE L. K/vA/ P,

ATTORNEYS fzjolla APPARATUS FOR FBQHSHING METALLIC COATING ON A FERROUS STRAND CROSS REFERENCE TO RELATED APPLICATION paratus for Finishing Metallic Coating on a Ferrous Strand".

BACKGROUND OF THE INVENTION This invention has great and particular utility in the finishing of a molten zinc coating applied to high carbon steel wire (above 0.45 percent carbon) for heavy duty applications. While this specification will therefore be primarily concerned with this embodiment of the invention, it should be understood that the apparatus taught herein is useful in the finishing of other molten metallic coatings on any cylindrical strand such as wire or tubing.

An exemplary product is the steel core wire for ACSR. It must have a very high tensile strength (a minimum of l60,000 psi) and should possess a high degree of corrosion resistance. In some cases, the strands must be guaranteed for 30 to 50 years. To these ends, conventional practice calls for the utilization of a metallic coated steel core wire-the tensile strength set forth above being imparted by the starting material, and the corrosion resistance obtained by the metallic coating.

According to ASTM designation for Class A coatings, steel core wire for ACSR having a diameter in the range of 0.104 inches to T1 19 inches must have a minimum coating weight of 0.80 ounces per square foot of uncoated wire surface (ASTM designation 8245-63). According to the prior art, zinc coating weights in this range have been obtained only at relatively low wire speeds.

For example, the prior art has successfully produced a product having the necessary characteristics by utilizing a charcoal bed nominally 3 inches thick floating on the surface of the coating bath, and withdrawing the coated strand through this charcoal bed. The charcoal bed effects a wiping action on the coating adhering to the strand, but will permit sufi'lcient coating to remain on the strand to meet the coating requirements. set forth above. Commercial experience with this operation has indicated that wire speeds on the order of 65 to 80 feet per minute are feasible. At higher speeds, the coating adhering to the wire will drag charcoal out of the bed and give a rough coating.

It is also known in the art to provide a finishing die in place of the charcoal bed to provide desirable surface characteristics to the metallic coating. According to general practice, such finishing dies are spaced a short distance above the normal surface level of the coating metal bath, and serve to catch the oxide sock formed on the surface of the bath and prevent its withdrawal on the strand. This practice is widely used in connection with low and intermediate weight aluminum coatings applied to low carbon wire.

Accordingly, the primary object of this invention is to provide an apparatus for finishing the molten coating adhering to a steel core wire, which will give heavy coating weights, good surface characteristics, and permit high speeds of operation.

SUMMARY OF THE INVENTION This invention contemplates the provision of a close tolerance die which is partly submerged in the bath of molten metal, and through which the wire is withdrawn from the bath at high speed. It is also contemplated that a non-oxidizing atmosphere will be provided for the coated wire for a short time period following its emergence from the die.

The apparatus of the invention includes the die as described in more detail hereinafter, and a holder in which the die is securely fastened. The holder is arranged for free movement in any direction in a single plane normal to the direction of travel of the wire, and is adjustable in a plane normal to the plane of movement to'control the relationship between the die and the level of coating metal in the bath.

DESCRIPTION OF THE DRAWING FIG. 1 is a front elevational view of the mounting arrangement for the die and holder of this invention.

FIG. 2 is a side elevational view of the mounting arrangement of FIG. 1 and showing the relationship of the die holder thereto.

FIG. 3 is a fragmentary cross sectional view on a greatly enlarged scale taken along the lines 3-3 of FIG. 1, and showing the details of construction of the holder and die.

DESCRIPTION OF THE PREFERRED EMBODIMENT The continuous hot dip coating of a steel base strand involves a preparatory treatment of the strand to render its surface receptive to the molten coating metal. That is, the surface of the strand must be suffrciently cleaned that an extremely rapid and thorough wetting by the molten coating metal takes place upon immersion into the coating bath.

Various preparatory procedures are well known in the art. One procedure in wide commercial use accomplishes the surface preparation by successive heat treatment of the strand in an oxidizing atmosphere wherein a thin, controlled oxide coating is formed on the strand, and in a reducing atmosphere wherein the previously formed oxide layer is removed. Such procedures are described in detail in Sendzimir US. Pat. Nos. 2,110,893, 2,136,957, and 2,197,662.

These procedures are highly advantageous for most metallic coating operations. However, they do involve relatively high temperatures during the reducing heat treatment in particular, and this high temperature level has a detrimental effect on the original mechanical properties of the base strand. Thus, these procedures are somewhat less desirable for the instant process wherein retention of the starting properties of the strand is necessary.

Other preparatory processes, and specifically the process best suited for the instant invention involve the utilization of complex salts as a flux. Specifically, the strand is passed through an acid cleaning bath, a rinse to remove the greater portion of the acid from the strand, and then a flux bath such as zinc ammonium chloride. Upon emerging from the flux bath, the strand is heated to dry the flux carried out of the bath by the strand, and the strand is then passed into the molten metal coating bath.

The preparatory steps generally described above do not per se form a part of this invention, but it will be understood that suitable surface preparation is a prerequisite to the practice of this invention. It will be assumed for purposes of the following description that the surface of the strand has been adequately prepared by some procedure conforming to the steps outlined above.

Turning first to FIG. 3, the molten metal coating bath is indicated at 10, and the ferrous base metal strand at 12. It will be seen that the strand 12 is withdrawn from the bath in a vertically upward path of travel. It is generally recognized that in the coating of a cylindrical strand, the vertical path of emergence from the coating bath is desirable in that the natural forces of gravity and inertia do not tend to destroy concentricity between the strand and the metallic coating.

As seen in FIG. 3, the strand E2 is withdrawn from the coating bath through a close clearance die indicated generally at 14. The die 14 should be made of a refractory material which is not readily wettable by molten zinc. As generally indicated above, the aperture 16 of the die 14 has a rather small clearance around the wire being coated. It has been determined that the clearance of the passage 16 over the wire 12 should be not more than 50 percent of the diameter of the base strand. ln terms of commercial practice, a clearance of about 0.030 to 0.035 inch (0.762 to 0.889 mm.) clearance on a diameter of 0.132 inch (3.353 mm.) has been found to be successful in producing a Class A coating. (About 24 percent of the diameter of the base wire).

It will also be observed that the entrance edge 18 of the aperture 16 is sharp. As used in this specification, the phrase sharp entrance edge" includes two important elements. First of all, the angle between the wall of the passage 36 and the entrance face of the die must not be more than 90. That is, if this angle were greater than 90, there would in effect be a bell shaped entrance into the die which would permit the accumu lation of dross, oxides, and the like at the entrance to the bore. Secondly, the phrase sharp entrance edge requires that there be substantially no radius at the edge 18. This sharp entrance edge is necessary in order to peel off any oxide which might otherwise be carried out of the bath by the moving strand.

Still referring to FIG. 3, it will be seen that the die 14 is secured in a counterbore 22 in the holder indicated generally at 20. The die is securely fastened to the holder by means of the set screw 24.

The upper portion of the holder 20 is provided with the aperture or passage 26 which defines a chamber adjacent the exit side of the die 14 and in which a non-oxidizing atmosphere is maintained. This atmosphere is introduced into the chamber via the pipe 28 and passage 30 in the wall of the holder 20. In a commercial operation utilizing this invention, natural gas can be supplied through the pipe 28 and passage 30, and ignited at the open end of the aperture 26. The pressure of the gas is low enough that it exerts no noticeable effect on the metallic coating, other than, of course, the provision of the non-oxidizing atmosphere.

It will also be seen that the holder 20 is provided with an elongate member 32 projecting therefrom in a plane normal to the path of travel of the wire.

The mounting means to receive the holder described above is shown in FIGS. 1 and 2 and, generally considered, is arranged to permit movement of the holder in any direction in a plane normal to the path of travel of the wire. The mounting means is also arranged to provide adjustable motion of the holder in a plane parallel to the path of movement of the wire in order to control the relationship between the level of molten metal in the bath and the position of the die.

As seen in FIGS. 1 and 2, the mounting means includes a horizontal member 34 carrying on its lower surface a plurality of spacer blocks 36. These spacer blocks 36 are of substantially the same thickness as the elongate member 32 of the holder 20. Fixedly secured to the lower edge of the spacer blocks 36 are the horizontal members 38. It will be apparent that the horizontal members 34 and 38 define therebetween a horizontal slot and, as seen in FIG. 3, this slot slidingly receives the elongate member 32 of the holder. It will be apparent from a consideration of these figures that this arrangement will permit universal motion of the holder in a plane normal to the path of travel of the wire, and will constrain the holder against movement paralleling the path of travel of the wire.

According to the preferred embodiment of the invention, the mounting means described above is of a width to accommodate a plurality of holders. As seen in FIG. 1, one such holder is shown in place. When a plurality of holders are provided, it will be apparent that the width of the slot must be sufficient to permit rela tive movement between the holders slidingly engaged therein.

Secured to and extending upwardly from the horizontal member 34 are the locking clips 40 and gusset braces 42. These locking clips may be releasably secured by means of the bolts 44 to any suitable frame adjacent the coating pot. The frame in the drawings is generally indicated at 46.

Also secured to the frame 46 are a pair of internally threaded lugs 48. These lugs 48 receive the adjusting screws 50, the lower end of which is rotatably secured to the horizontal member 34 by the keeper bolts 52.

It is believed that operation of the mounting means should be clear from the foregoing description. When the bolts 44 are loosened, the adjusting screws may be actuated by any suitable device to raise and lower the horizontal members 34 and 38 (and of course the slot defined therebetween) so as to vary the vertical position of the holder with respect to the coating metal bath. Once the desired position has been set, the mounting means is locked in place by means of the bolts d4.

As seen in FIG. 3, the preferred vertical adjustment of the mounting means is such that at least a portion of the lower end of the holder 20 and die 14 are submerged in the coating metal bath. The preferred range of submersion is on the order of one-eighth to onefourth inch (3.2 to 6.4 mm.). While the precise amount of submersion is not critical, it is very important that the die always be maintained submerged in order to prevent the oxide coating which forms on the surface of the bath from getting to the entrance face of the die.

It is believed that the foregoing constitutes a full and complete disclosure of this invention. While it has been described in terms of an exemplary embodiment, it

should be understood that no limitations are to be inferred or implied except as specifically set forth in the claims which follow.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for the continuous coating of a ferrous strand including means for cleaning the surface of the strand to render said surface receptive to the coating metal, a bath of molten coating metal, and means for moving said strand through said cleaning means and said bath, the improved finishing apparatus comprising:

a. a die having an aperture for the passage of said strand therethrough;

a holder for said die including means for securing said die therein and including an arm of relatively narrow width, extending horizontally therefrom;

and

c. mounting means for said holder permitting free floating movement of said holder in any direction in a plane normal to the path of movement of said strand and maintaining at least a portion of said die immersed in said bath said mounting means ineluding a relatively wide, horizontally extending slot through which said arm extends, said arm and said slot having a close, sliding fit whereby to maintain said free floating planar holder movement.

2. The apparatus claimed in claim 1 wherein said holder includes a portion defining a chamber adjacent the exit side of said die, and including means for maintaining a non-oxidizing atmosphere in said chamber.

3. The apparatus claimed in claim 1 including means for adjusting the position of said mounting means in a plane normal to the plane of movement of said holder.

4. The apparatus claimed in claim 1 wherein said slot is of a width to accommodate the elongate members of a plurality of said holders.

5. The apparatus claimed in claim 1 wherein the aperture in said die has a sharp entrance edge.

6. The apparatus claimed in claim 2 wherein said means for maintaining a non-oxidizing atmosphere in said chamber includes a passage in said portion of said holder communicating with said chamber, said passage being directed at the areas of said aperture in said die.

7. The apparatus claimed in claim 1 wherein the clearance between said aperture and said ferrous strand is not more than 50 percent of the diameter of said strand. 

1. An apparatus for the continuous coating of a ferrous strand including means for cleaning the surface of the strand to render said surface receptive to the coating metal, a bath of molten coating metal, and means for moving said strand through said cleaning means and said bath, the improved finishing apparatus comprising: a. a die having an aperture for the passage of said strand therethrough; b. a holder for said die including means for securing said die therein and including an arm of relatively narrow width, extending horizontally therefrom; and c. mounting means for said holder permitting free floating movement of said holder in any direction in a plane normal to the path of movement of said strand and maintaining at least a portion of said die immersed in said bath said mounting means including a relatively wide, horizontally extending slot through which said arm extends, said arm and said slot having a close, sliding fit whereby to maintain said free floating planar holder movement.
 2. The apparatus claimed in claim 1 wherein said holder includes a portion defining a chamber adjacent the exit side of said die, and including means for maintaining a non-oxidizing atmosphere in said chamber.
 3. The apparatus claimed in claim 1 including means for adjusting the position of said mounting means in a plane normal to the plane of movement of said holder.
 4. The apparatus claiMed in claim 1 wherein said slot is of a width to accommodate the elongate members of a plurality of said holders.
 5. The apparatus claimed in claim 1 wherein the aperture in said die has a sharp entrance edge.
 6. The apparatus claimed in claim 2 wherein said means for maintaining a non-oxidizing atmosphere in said chamber includes a passage in said portion of said holder communicating with said chamber, said passage being directed at the areas of said aperture in said die.
 7. The apparatus claimed in claim 1 wherein the clearance between said aperture and said ferrous strand is not more than 50 percent of the diameter of said strand. 